Among semiconductor devices including a semiconductor element, a pair of heat radiating plates for radiating heat from both surfaces of the semiconductor element, and an encapsulating resin for covering all over the device, there has conventionally been a semiconductor device that further includes a solder layer for bonding the semiconductor element and the heat radiating plates and a polyamide resin that is applied to surfaces of the heat radiating plates and improves adhesion to the encapsulating resin. The heat radiating plate is connected to a terminal of the semiconductor element and also utilized as an electrode (see Patent Document 1, for example).